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How big was Hudiesaurus?

January 17, 2008

In the last post, an astute commenter asked about Hudiesaurus: “A first dorsal 550 mm–isn’t that in Argentinosaurus territory?”

Well, let’s find out.

Hudiesaurus sinojapanorum was described by Dong (1997) based on a partial skeleton from the Kalazha Formation in China. The holotype, IVPP V 11120, is an anterior dorsal vertebra. Referred elements include a nearly complete forelimb, supposedly from a smaller individual of the same taxon.

I don’t actually have a copy of Dong (1997), but I do have Glut (2000), which contains a pretty good summary and a couple of pictures. Here’s the holotype dorsal in posterior view, after Glut (2000), after Dong (1997).

According to Glut, the scale bar is 15 cm–I added the “15 cm” in the image above for ease of use. Presumably ‘sp’ is ‘spine’, ‘po’ is ‘postzygapophysis’, ‘dp’ is ‘diapophysis’, and ‘ce’ is ‘centrum’. Glut says:

As measured by Dong (1997), the holotype dorsal centrum of H. sinojapanorum has a length of 42 cm, 1.5 times longer than the comparable element in the 22-meter (about 75-feet) long mounted holotype skeleton of Mamenchisaurus hochuanensis, which was the largest sauropod known from China when it was described. From these dimensions, Dong (1997) estimated the total length of H. sinojapanorum to be about 30 meters (more than 100 feet) in length.

IF the scaled figure (from Glut [from Dong]) is accurate, and if the 42 cm length (reported by Glut [reported by Dong]) is accurate–and the uncertainties involved cannot be ignored, especially after the last post–then the vertebra has the following dimensions:

Centrum length: 42 cm

Cotyle height: 39 cm

Cotyle breadth: 42 cm

Total height: 78 cm

None of these are close to 550 mm, so there’s no telling where that measurement came from or what it refers to.

UPDATE: please read comment #4 below, by Mickey Mortimer, which sets the measurement record straight. And invalidates the specific numbers used in the rest of the post, but not the overall point.

Fortunately for us, the dimensions of the vertebrae of Mamenchisaurus hochuanensis are available for free in English, along with the rest of the description (Young and Zhao 1972), courtesy of the wonderful Polyglot Paleontologist site. Here’s the paper. Let’s do some comparin’.

D1 of M. hochuanensis has a centrum length of 25 cm, cotyle height of34 cm, cotyle width of 17 cm, and total height of 64 cm. The fact that the centrum is twice as tall as wide is almost certainly an artifact of the lateral compression that affects the whole vertebral column to some extent. Let’s say for the sake of argument that the cotyle was originally circular and 25 cm in diameter. The holotype of H. sinojapanorum is 68% longer, 60% larger in diameter, and 22% taller. So if the vertebra is actually D1 and if H. sinojapanorum was built like M. hochuanensis (be sure to keep your If Counter updated), it might have been anywhere from 27-37 meters long (89-121 feet).

A couple of points before we go on. First, that’s pretty big, but it’s also a huge range. At the low end, it’s no bigger than Diplodocus; at the high end, it’s one of the longest sauropods on record. So that math suggests that it was a big sauropod but doesn’t help us pin down how big it was. Second, you have to keep in mind that Mamenchisaurus hochuanensis is basically a ridiculous neck attached to an unremarkable body (at least in terms of size). If you ignore the neck, the animal was about the same size as Cetiosaurus or Haplocanthosaurus–about 75% the size of the well-known specimens of Apatosaurus, Diplodocus, and Camarasaurus, and no where near the size of Brachiosaurus (despite having a longer neck). It’s basically a weiner dog, with most of the weiner out in the neck. Which is how Hudiesaurus could be 22% bigger and still be about the same size as Diplodocus. Even if Hudiesaurus was 60% bigger than M. hochuanensis, it would still not be in Argentinosaurus range in anything but length.

Mike (white shirt on lift) with M. hochuanensis at the Field Museum. It is worth remembering that he would need the same lift at about the same height to work on the posterior cervicals of Brachiosaurus!

Also, assigning serial positions to isolated vertebrae is tough. What if Dong was off by a single position, and the holotype vert is actually the most posterior cervical? True, it doesn’t have fused cervical ribs, but cervical ribs can fuse pretty late in ontogeny. Furthermore, rib identities can get a little wonky in the cervico-dorsal transition. Sometimes you have a nice, well-behaved, fully-fused rib on the last cervical, and a nice, well-behaved, long mobile rib on the first dorsal, but sometimes there is a godawful Frankenstein rib that doesn’t fit neatly into either category. Anyway, we’re just playing “what if” here. Nobody should take this as gospel.

The last cervical of M. hochuanensis has a centrum length of 32.5 cm, an average cotyle diamter of 29 cm, and a total height of 66 cm. If the holotype of Hudiesaurus actually corresponds to this vert instead of D1, then it is 29% longer, 38% larger in diameter, and 18% taller. In other words, no bigger than Diplodocus. In which case, the articulated forelimb might belong with the dorsal vertebra after all. Although it was found more than a kilometer away from the vertebra, so the case for it’s referral to the same taxon is not strong. At all.

But that’s not all! Not all Chinese sauropods were hellaciously long-necked, a point made by Mickey Mortimer in his DML post on Hudiesaurus. Abrosaurus ha 13 cervicals, rather than 19 like M. hochuanensis, and its cervicals are only about a third longer than its dorsals (upshot: in neck-to-body proportions, it was built like Camarasaurus). If Hudiesaurus was built like a giant Abrosaurus, it might have approximated a large individual of Camarasaurus in both body size and neck length.

A final amusing point. Glut (2000, p. 235) includes a photograph of the articulated forelimb of Hudiesaurus on display at Dinofest ’98 in Philadelphia. Next to the forelimb is a string of 4 articulated dorsal vertebrae. What is this? The original paper only mentions one dorsal vertebra, so where did the other three come from? Sadly, they came out of the same mold as the first–if you look carefully at the photo, you can see that the exhibitors simply made four casts of the same vertebra and strung ’em together to look like something more complete.

It’s not uncommon to clone adjacent vertebrae to fill out mounted skeletons. Heck, the T. rex skeleton in the Valley Life Sciences Building at Berkeley (my old digs) has a block of 5 identical dorsals, and its caudals come in identical pairs all the way down the tail (easy to see even in the small photos here). But that’s a different case. T. rex is known from complete remains, and the cloning was only done to fill out a skeleton that was already mostly there. The exhibition of the cloned Hudiesaurus vertebrae bothers me, because it implies to observers that the animal is better known than it actually is. I wasn’t at Dinofest ’98 so I can’t tell you for certain that there wasn’t a sign right there that said, “Warning: this animal is based on one vertebra that we have cloned to show you what a string of them would look like!” but I seriously doubt that there was any indication at all (that’s no reflection on Dong; he probably had nothing to do with the choices made by the exhibitors).

Here’s the take-home message:

If you see an eyebrow-raising number tossed out regarding a giant dinosaur, don’t surrender your credulity until you or someone you trust have tracked down the sources. And anytime you see mounted material, it’s perfectly fair to ask how much of it is real.

17 Responses to “How big was Hudiesaurus?”

When I said Argentinosaurus territory, I remember reading another Mortimer post on the DML and remember the vertebra apparently being that sort of length. I’ve never actually seen the paper describing the animal. (Apart from the images that were posted previously).

The post certainly highlights the many problems with trying to visualise specimens that are only known from very few bones and then extrapolating from relatives. Anyhow, this size stuff fascinates me. Maybe it’s because it’s relatively simple compared to say, the classification side of palaeontology, which I’ve never gotten around to studying properly. Cheers!

When I said Argentinosaurus territory, I remember reading another Mortimer post on the DML and remember the vertebra apparently being that sort of length.

I didn’t quote you to mock you! :-) It’s a legitimate and interesting question. If you can dig up that other post, the one with the 550 mm measurement, I’d be interested in seeing it. FWIW, centrum length is a pretty lousy proxy for size, because vertebral proportions vary so much along the column and among taxa. It’s not completely uninformative–so far, everything with 1m-plus cervicals is pretty darn big–but it varies more than almost anything else so precision goes right out the window.

The post certainly highlights the many problems with trying to visualise specimens that are only known from very few bones and then extrapolating from relatives. Anyhow, this size stuff fascinates me.

Thanks, I feel the same way. On one hand, it is frustrating, because the biggest dinosaurs–the biggest land animals of all time–are only known from scraps. On the other hand, it’s exhilarating to think that the dinosaurs we think of as big–Apatosaurus, Diplodocus, Brachiosaurus–were really just the tip of the gigapod iceberg.

http://dml.cmnh.org/2003Dec/msg00163.html (The post is quite relevant to this topic) The Argentinosaurus verts are actually stated as being around 450 -500mm. Not shure whether that the whole vert or just the centrum. As for the 550mm for Hudiesaurus, maybe that figure is the total length rather than just centrum length.

‘it is frustrating, because the biggest dinosaurs–the biggest land animals of all time–are only known from scraps’

The scale bar for the figure you posted (fig. 3 in Dong’s paper) is actually 14 cm, not 15 cm. So Glut made a mistake. Also you can see the 42 cm measurement was anterior central width, not central length, so Glut erred there as well. You weren’t joking about the perils of ignoring those uncertainties! ;) There’s a photo of the vertebra in lateral view (fig. 1) with a scale bar included which would indicate the centrum is 52.3 cm long. Which isn’t far off from the measurement table.

In the discussion, Dong states the centrum is 1.5 times longer than the M. hochuanensis holotype, but it seems 2.2 times longer to me based on Young and Zhao’s paper. Then again, the vertebrae is only 1.19 times taller and the cotyle is 1.56 times wider. Compared to Young and Zhao’s figure of dorsal 2, Hudiesaurus’ is quite a bit longer compared to centrum height. Maybe your idea of it being a last cervical is correct. The height/centrum length ratio of Hudeisaurus’ vertebra is intermediate between the 17th and 18th cervicals of Mamenchisaurus. But I’m no sauropod expert, so I wouldn’t know what other details to look for.

Many thanks for weighing in. It is interesting that the measurements I took off the figure are so close to what Dong reported, despite the fact that I was using an incorrect scale bar.

An animal built like Mamenchisaurus but 1.5 times larger would have a neck 14m long, which is out there in Supersaurus territory. It’s certainly not implausible that such a creature existed (well, no more implausible than any of the rest of these giant sauropods). But as you pointed out in your DML post, we should not forget about Abrosaurus…

May I join the conversation as an intrigued passer-by? I’m not employed in science, but a 1982 Zoology degree and ongoing fascination with dinosaurs are my excuses..

‘Abrosaurus has 13 cervicals, rather than 19 like M. hochuanensis, and its cervicals are only about a third longer than its dorsals.. If Hudiesaurus was built like a giant Abrosaurus, it might have approximated a large individual of Camarasaurus in both body size and neck length.. Also, assigning serial positions to isolated vertebrae is tough..’

It’s interesting to consider that partial remains may leave much scope for such variant reconstructions. And that new incomplete finds may not have had the same proportions as species already known.. even those species judged to be most similar on the basis of particular (equivalent?) bones.

Re that photo of M. hochuanensis, it may be a naive comment but am I alone in thinking how flimsy the leg bones look compared to the neck? (especially those last few cervicals.. pleurocoels there I know, but still awesome). Femur and humerus in particular seem mere sticks by comparison!

It makes me wonder how these creatures could manage to squat, kneel or lie down – let alone mate! – and how slowly they may have moved… it’s not just their weight, it’s the inertia and angular momentum, torque and leverage, that I’m thinking of.

The seeming gracility of the Mamenchisaurus hochuanensis humeri and femora, and the seeming robustness of its cervicals, are both illusions.

In most sauropods, M.hoch included, humeri and femora are both anterolaterally compressed, so that their transverse width is about twice their anteroposterior width. Take a look at the photo at http://www.miketaylor.org.uk/dino/mamenchi/page/16.html , which is of another cast of precisely the same specimen of M.hoch. From this anterolateral perspective, the humeri look very robust.

The cervicals look robust from the side for several reason. First, they are noticably taller than they are wide, so the same neck looked at from above would appear a lot thinner. Second, crushing in this particular specimen exaggerates the degree of eccentricity to make the cervicals look even taller than they were in life. Third, although they encompassed a lot of space, they were very lightly constructed and largely filled with air — whereas in this specimen all the air-spaces are filled with matrix, making them appear solid.

So the legs are much more solid, and the neck much less so, than you’d think from the photo above.

By the way, the FMNH staff were fantastically helpful when we visited — I’ve never known anything like it. They brought that cherry-picker thing into the museum just for us, so I could get up close and personal with the cervicals. They also disassembled a huge display cabinet so we could get at the Brachiosaurus altithorax type humerus. Happy days. Not only that, in a sushi restaurant just across the park from the museum, we ordered a Gozilla Roll, which may be the single most wondrous thing I have ever tasted.

The problem I’ve found with scale bars in pictures — at least the way I take them — is that when photographing small things, any scale bar placed physically in the field with the object and photographed is nearly in the same plane as the object, thus making the scale bar much more applicable to the object itself. When dealing with much larger (at least, much thicker) objects, like sauropod vertebrae…for example, if one puts the vert in position for, say, a right lateral view (such that one has had to place a bunch of blocks under the vertebral body [er, “centrum”] so that the thing isn’t sitting at an angle because of the transverse process), and then puts the scale bar on the floor next to it, then the camera focuses on the right-hand surface of the vertebra, but the scale bar is in the same plane as the left-hand side of the vertebra. In short, it’s farther away, and therefore appears (in a two-dimensional view) smaller. I’ve never calculated, or seen calculated, how big a difference this is (probably only a few percent), but I’ve often wondered if it can add up to increasingly substantial errors… Which leads to the question, then, of where’s the best place to put the scale bar? Should it, too, be elevated, and, if so, to where? The same plane as the vertebral body? The “highest” point of the vertebra (in the case above, to the top of the right transverse process) in the picture? Of course, this really is just a function of the fact that different parts of a vertebra are also going to be distorted in such a perspective (like Luis Rey’s pictures in Holtz’s new book, where the heads of the animals seem ginormous because the heads are closer to the viewer than the rest of the bodies are — personally, I really don’t like those kinds of pictures, even though they’re perfectly valid perspectives!) — the parts closer to the camera will appear huge and the parts farther away will appear tiny, but clearly a scale bar in any one plane doesn’t apply to each part — only to those parts in the same plane as the scale bar itself!

I mention all this only to suggest that this might be a part, if not the entirety, of the difference between reported measurements and measurements taken from photos with a scale bar. And, of course, if one uses something like Photoshop to replace the actual scale bar with a solid black or white bar instead, an additional error (albeit again probably small but measureable) is introduced by trying to approximate which column or row of pixels really equals the end of the mark on the scale bar and should therefore also be the end of the digital “replacement” bar…

I’d be interested to know how others do their scale-bars. I find it useful to have a physical scale-bar in shot for one or more photos, but not to rely-on — only for sanity-checking. Instead, I draw the scale-bar by hand onto the figure, based on measurements whose accuracy I am confident of. It’s nice to see when these pretty much tally with the bars in the original photo.

How about placing lightweight spheres – of a stated diameter, say 100mm or 200mm – at various locations around a specimen (or at least bracketing it) if different parts are going to be at significantly different distances when photographed?

A sphere has the advantage of looking the same whatever the viewing angle. Its diameter is thus easily compared for scaling of the object.

Any pictures with Daleks in are handy for scaling nearby objects… all those 4inch domes…

Mike, thanks a lot BTW for your welcome above and your detailed reply to my question! Yes, I see those leg bones are much wider transversely. Interesting, in itself…

I would love to know more about their range of motion in life – did these animals kneel or lay down sometimes, or were they basically on their feet for life? How straight, and how vertical, did they normally keep their limbs? How readily could they turn?

Or …back on the topic of vertebrae!… how did those necks behave?

All this is of more than usual interest to me just now, as I am considering the practicability of sauropods going on parade locally in August: for Dunfermline’s inaugural Carnegie Festival of the Imagination.

Diplodocus carnegii and Apatosaurus louisae, being named after Andrew Carnegie and his wife Louise, and now approximately centenary, seem apt subjects for a festival here in his home city…

…if a mite challenging…

I suspect any parade versions may have to be rather more pneumatic than the originals!

[…] impossible, since 30-foot-plus necks are known for the largest individuals in several clades (e.g., Mamenchisaurus, Supersaurus, Sauroposeidon, probably Puertasaurus, possibly Futalognkosaurus, but probably not […]

[…] of the recently-described giant sauropods from China, trying to sort out just how big they were. Not a new pursuit for me, just one I hadn’t been back to in a while. Also, I’m not trying to debunk anything […]